This application is based upon and claims the benefit of priority of Japanese Patent Applications No. H.11-98864 filed on Apr. 6, 1999 and No. H.11-166081 filed on Jun. 11, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a wiper device for vehicles in which a:wiper:blade may be easily attached to and detached from a wiper arm.
2. Description of Related Art
In a wiper device for wiping a wind shield glass of a vehicle, a wiper blade is rotatably held by a wiper arm. Generally, the wiper blade is held by the wiper arm in such a manner that a holding clip for holding the wiper blade is.mounted on the wiper arm by a supporting shaft and a letter U shaped leading end portion of the wiper arm is retained to the holding clip.
However, as the holding clip becomes necessary in order for the wiper arm to hold the wiper blade, more number of component parts and more fabrication times-are required, thus resulting in higher cost.
To cope with this problem, proposed has been a wiper device, as shown in JP-A-6-156200, in which the wiper arm and blade are easily attachable and detachable with less number of component parts so that the cost may become less. According to this wiper device, a supporting shaft directly bridges the opposite side walls of the wiper blade in a width direction and the leading end portion of the wiper arm is elastically and rotatably connected to the supporting shaft. Further, the rotating movement of the wiper blade relative to the wiper arm is restricted in a way that the leading end portion of the wiper arm comes in contact with the wiper blade.
However, the connection of the wiper blade with the wiper arm relies upon elastic supporting force on the supporting shaft provided at the wiper blade. Therefore, when a strong rotating force is applied to the wiper blade, though the leading end of the wiper arm comes in contact with the wiper blade and the rotating movement of the wiper blade is restricted, there is a risk that the contacting point between the wiper arm and the wiper blade acts as a fulcrum so that the leading end portion of the wiper arm may be unexpectedly detached from the supporting shaft by the strong rotating force against the elastic supporting force on the supporting shaft. As a result, the wiper blade and the wiper arm are likely to be separated from each other.
The present invention has been made in view of the above mentioned problem, and an object of the present invention is to provide a wiper device for vehicles having a simple construction that the wiper blade is easily attached to and detached from the wiper arm but the wiper blade and the wiper arm are rotatably coupled not to be disengaged with each other in a normal use of the wiper device. In the wiper device, when the wiper blade is detached from the wiper arm for a purpose of the maintenance, an excessive rotating movement of the wiper blade relative to the wiper arm is adequately restricted so that not only the wiper arm and blade may not be harmed, but also a vehicle body or a window glass may be prevented from damages.
To achieve the above object, the wiper device has a center bore provided in a center portion of the wiper blade, a supporting shaft extending transversely to a longitudinal axis of the wiper blade in the center bore and a connecting hole provided transversely to a longitudinal axis of the wiper arm at a leading end portion of the wiper arm. The supporting shaft has first and second diameter portions extending respectively in an axial direction thereof at a circumference thereof and a diametric length of the second diameter portion is smaller than that of the first diameter portion. The connecting hole is provided at a circumference thereof with an opening whose chord length is larger than the diametric length of the second diameter portion but smaller than the diametric length of the first diameter portion.
With the construction mentioned above, the wiper blade may be attached to and detached from the wiper arm by making the second diameter portion correspond to the opening and moving the second diameter portion through the opening into and out of the connecting hole in the center bore, but the wiper blade may not be detached from the wiper arm in a normal use of the wiper device by rotating the wiper blade relatively to the wiper arm till a position where the second diameter portion does not correspond to the opening in the connecting hole.
As mentioned above, for coupling the wiper blade with the wiper arm, the position of the second diameter portion relative to the opening defines an attachable and detachable region and a non-attachable and non-detachable region for the wiper arm and blade. The attachable and detachable region covers a first predetermined angle zone of the wiper blade to the wiper arm where the second diameter portion corresponds to the opening. The non-attachable and non-detachable region covers a second predetermined angle zone of the wiper blade to the wiper arm where the second diameter portion does not correspond to the opening due to rotating the wiper blade relatively to the wiper arm from the first predetermined angle zone. The second predetermined angle zone is used in a normal use of the wiper device.
As a result, the coupling of the wiper blade with the wiper arm can not be disengaged during the normal use of the wiper device but the wiper blade can be easily attached to and detached from, the wiper arm without large force by rotating the wiper blade relatively to the wiper arm when the wiper blade is replaced for maintenance purpose.
Further, according to the embodiment mentioned above, different from the conventional unstable coupling that the supporting shaft is held by an elastic force, the coupling construction of the present invention is so stable that the wiper blade may not be unexpectedly disengaged and separated from the wiper arm during the normal use thereof.
It is an another aspect of the present invention to provide elastically deformable restraining means at the wiper arm and blade for restraining an excessive rotation of the wiper blade relative to the wiper arm during the normal use of the wiper device from the second predetermined angle zone to the first predetermined angle zone. Thus, the second diameter portion may not correspond to the opening and the wiper blade may not be detached from the wiper arm once the wiper arm and blade are placed at the second predetermined angle zone.
The elastically deformable restraining means serves to prevent not only damages of the vehicle body or wind shield glass but also an easy disengagement of the wiper blade with the wiper arm, due to unintentional excessive rotation of the wiper blade relative to the wiper arm, for example, when the wiper arm is rocked back for a purpose of maintenance. However, if the excessive force is applied intentionally to the elastically deformable restraining means in such a case that the wiper blade is replaced for maintenance, the coupling of the wiper blade with the wiper arm may be disengaged without harms of the wiper arm and blade.
The elastically deformable restraining means is preferably composed of an elastically deformable element disposed at any one of the wiper arm and blade and a restraining element disposed at the other of the wiper arm and blade. The elastically deformable element is engaged with the restraining element between the first and second predetermined angle zones.
Preferably, more than half of an outer circumference surface of the supporting shaft in the connecting hole comes in sliding contact with an inner circumference surface of the connecting hole in the normal use of the wiper device.
With the construction mentioned above, even if the supporting shaft has the second portion whose diametric length is smaller than the length of the opening, the supporting shaft stays stable in the connecting hole not to come out of the connecting hole through the opening and does not rattle in the connecting hole in the normal use of the wiper device.
Generally, the center bore and the supporting shaft may be provided at a center portion of a lever assembly (primary lever) of the wiper blade. However, in case of the wiper blade having a lever assembly, a clip holder fixed to the lever assembly and a blade rubber held by the lever assembly for wiping the wind shield glass, the center bore and the supporting shaft may be disposed in the clip holder.
Furthermore, in a case that the center bore has an inner wall facing to a leading end surface of the wiper arm, it is preferable that a clearance between an upper periphery surface of the inner wall and the leading end surface of the wiper arm is not larger than a clearance between the other surface of the inner wall and the leading end surface of the wiper arm. This construction is effective to prevent snow, stone pieces or other foreign material from being stuck in the clearance between the surface of the inner wall and the leading end surface of the wiper arm.
To achieve this construction, the surface of the inner wall is formed in an inclined shape or in an arc shape having a center on an axis of the supporting shaft, or a projecting portion protruding toward the leading end surface of the wiper arm is provided at the upper periphery portion of the inner wall.
Furthermore, in addition to the construction mentioned above, it is more preferable that the surface of the inner wall overlaps at least partly the leading end surface of the wiper arm as viewed perpendicularly to the longitudinal axis of the wiper blade so that a view through the clearance from one side to the other side may be obstructed. To this end, the leading end surface of the wiper arm is preferably shaped as an arc having a center on a center axis of the connecting hole concentrically with that of the surface of the inner wall.